Safety clutch

ABSTRACT

A safety clutch to be used in conjunction with a horizontal earth boring machine. The clutch is located between the boring machine and the auger. The clutch acts as a safety device to prevent over-turning of the boring machine when the auger becomes bound in the earth, prevents stalling of the drive unit, and limits the loadings on the power-train elements and the auger. The safety clutch comprises a drive plate compressed between friction disks having resilient backing elements. These friction disks and backing elements are fixed to the driven side of the clutch.

[ 1 Dec. 4, 1973 Century et al. I

I SAFETY CLUTCH [75] Inventors: Bernard A. Century, Cleveland Heights;Michael Linsay, South Euclid, both of Ohio [73] Assignee: Allied Steel &Tractor Products,

Incorporated, Cleveland, Ohio 22 Filed: Apr. 14,1972 2'11Appl.No.:244,023

[52] US. Cl. 64/30 D, 64/30 C, 64/13 [51] Int. Cl. Fl6d 7/02 [58] Fieldof Search 64/30 C, 30 D, 30 R,

[56] References Cited UNITED STATES PATENTS 3,118,292 1/1964 Schroter etal. 64/30 C 2,561,830 7/1951 Venderzec 64/30 D 2,801,535 8/1957 Cockery64/30 R 3,100,974 8/ 1963 Wilson et a]. 64/30 C FOREIGN PATENTS ORAPPLICATIONS 774,720 5/1957 Great Britain 64/30 C 1 PrimaryExaminer-Charles J. Myhre Assistant Examiner-Randall HealldAttorney-Charles G. Lyon et al.

: [5 7] ABSTRACT A safety clutch to be used in conjunction with ahorizontal earth boring machine. The clutch is located be-' tween theboring machine and the auger. The clutch acts as a safety device toprevent over-turning of the boring machine when the auger becomes boundin the earth, prevents stalling of the drive unit, and limits theloadings on the power-train elements and the auger. The safety clutchcomprises a drive plate compressed between friction disks havingresilient backing elements. These friction disks and backing elementsare fixed to the driven side of the clutch.

17 Claims, 5 Drawing Figures Ii L m mmanw g,

PATENTEU SHEET 2 0F 2 SAFETY CLUTCH BACKGROUND OF THE INVENTION Thisinvention relates to a safety clutch for a horizontal earth boringmachine which is capable of absorbing shock loading and minormisalignments without imcally contains a motor for driving the auger andmeans for powering the advancing mechanism. A necessary element of thesemachines is a clutch operably connecting the power train elements to theauger. These clutches are needed to prevent the over-turning of theearth boring unit when the auger becomes bound in the earth. Where theboring unit is sufficiently anchored to prevent the over-turning of thehousing, the clutch is needed to prevent the motor from stalling.

The clutches heretofore employed for horizontal earth boring machineshave typically used a driven plate which is clamped between phenolicdisks. The phenolic disks are held in compression against the drivenplate by rigid plates attached to the power train. These phenolic disks,the rigid supporting outer plates and the driven plate as heretoforemployed have been incapable of absorbing quantities of energy necessaryto dissipate transient thrust-type shock overloads transmitted from theauger assembly. Consequently, the excessive shock loadings aretransmitted through the clutch assembly to the power-train elements andthe driving motor. This high shock transmission characteristic canresult in the premature failure of the power train and motor elements.

In addition, to thrust-type shock overloads experienced by the clutch,excessive side loadings and torques transmitted from the auger are alsoreceived. These loadings tend to create misalignment between the drivingand driven portions of the clutch unit. The clutches heretofore employedwith horizontal earth boring equipment are less able to accomodatemisalignment because of the rigid nature of these devices. Undue strainon the clutch components can result from misalignment as well as asubstantial change in the torque value at which the clutch will commenseto slip.

SUMMARY OF THE INVENTION An object of the present invention is toprovide a clutch which can reduce the effect of transient thrusttypeshock overloads transmitted from the auger string to the power trainelements. To accomplish this result, the present invention incorporatesa novel combination of elements which reduces the rigidity of the unitwhile enhancing its overall performance. In the clutch of the presentinvention, the phenolic disks are backed with a resilient material. Thisresilient material is capable of absorbing substantial quantities ofenergy transmitted from the auger string. In this way, shock overloadsare not transmitted through the clutch to the power train elements. Toaccomodate this resilient material which is not capable of performingthe actual clutching operation, the phenolic disks have been constrainedto rotate with the backing plates. In this way, frictional loads are notplaced on the resilient elements.

Another object of the present invention is to accommodate themisalignments imposed by torques and side loadings transmitted from theauger string. Because the resilient elements associated with thefriction disks increase the total elasticity of the unit, smallerinternal loads result from a given misalignment than would beexperienced in the more rigid units heretofore employed. Further, theresilient elements more evenly distribute thenormal pressure between thedrive plate and the friction disks under such misalignments.Consequently, misalignment problems are less likely to result incomponent failure and substantial deviations in the torque levels atwhich the clutch will commence to slip.

A third object of the present invention is to extend the fatigure lifeof the clutch components. The resilient nature of the backing for thefriction disks acts to absorb and dissipate shock energy. Because thisshock energy is not transmitted through rigid couplings to the clutchcomponents, the components are not subjected to forces of highinstaneous magnitude which are detrimental to the fatigue life of thecomponents. Consequently, the resilient backing material enhances thelife of the clutch as well as it performance. A fourth object of thepresent invention is to provide a less sensitive means for adjusting theclutch to proper pressure. The present invention employs the samemechanisms for clutch pressure adjustment. However, because of itselasticity, the introduction of the resilient backing material providesfor a buildup of compressive force across a larger displacement of theadjustment means.

As a result, each specific adjustment of the clutch pressure willrequire a greater change in the adjusting means. This results in agreater range of misadjustment available to the operator without causingsignificant over-pressure on the clutch.

Other and further objects and advantages of the present invention willbe made readily apparent from the following detailed description andaccompanying drawmgs.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERREDEMBODIMENTS Turning now to the drawings, the horizontal earth boringmachine 10is shown on rails 12 with a portion of the auger 14illustrated in place. A cover 16 surrounds the clutch assembly 18 andthe output coupling 20. Plates 22 rotatewith the drivemechanism to forcedirt through openings (not shown) provided in the cover 16.

Turning specifically to FIG. 4, input shaft 24 is rigidly fixed to thecircular clutch plate 26 by bolt 28 and collar 30. Collar 30 is weldedto the clutch plate 26. Keyway 32 is providedin collar 30 for key 34.Key 34 prevents relative rotation between the collar 30 and the inputshaft 24. The clutch housing 18 is rigidly fixed to the output coupling20 and rotates therewith. The clutch housing is comprised of a circularfront plate 36 and an annular cover 38. The annular cover 38 acts topromote alignment between the input and output portions of the clutch.When other means of insuring alignment are provided as in FIG. 5, theannular cover 38 becomes unnecessary. Holes 40 are drilled into thefront plate 36 to accommodate the load bolts 42. Eight bolts 42 areillustrated in FIG. 3. However, the number of load bolts 42 required mayvary and is dependent upon load requirements and convenience. It isbeneficial to have the load bolts 42 equally spaced about the frontplate 36 in order to provide uniform loading on the clutch. The bolts 42are threaded into a back plate 44. The back plate 44 is circular andfits within the annular cover 38. The back plate 44 has a hole 46centrally located therein to accommodate the input shaft 24 and thecollar 30. When the annular cover 38 is em ployed with the back plate44, the combination acts to maintain alignment .between the input andoutput portions of the clutch. Hole 46 acts. as a guide about collar 30to keep collar 30 and consequently clutch plate 26 concentric with theclutch. Clamped between the front plate 36 and the back plate 44 and arephenolic disks 48 and 50. The phenolic disks 48 and 50 are restrainedfrom rotational movement relative to the front plate 36 by dowels 52 and54 respectively. A plurality of these dowels 52 and 54 may be providedwhere necessary. The phenolic disk 48 and 50 are forced into contactwith the clutch plate 26 by tightening the bolts 42. Frictionalinterfaces are thereby created for the clutching operation. A raisedcircular portion 56 is provided on the circular clutch plate 26 toretain the phenolic friction disk 48 in alignment. The input shaft 24provides the alignment function for the phenolic friction disk 50. Aresilient disk 58 is positioned between the front plate 36 and thephenolic friction disk 48. A similar resilient disk 60 is positionedbetween the back plate 44 and the phenolic friction disk 50. Theseresilient disks.58 and 60 act to absorb thrust shock energy imparted tothe clutch and accomodate angular misalignments between the input andoutput portions of the clutch. A wide range of resilient materials maybe used for the disks 58 and 60. However, it has been found thatNeoprene having a Shore hardness of from 50 to 60 provides the bestresults.

The proper tension is obtained in the clutch by tightening the loadbolts 42 uniformly to compress the phenolic friction disks 48 and 50against the clutch plate 26. The degree of pressure to be applied to thedrive plate will depend upon the amount of torque required to stall theengine or tend to overturn the earth boring unit 10. The compressionmust be such that the clutch will commence to slip before sufficientbinding torque is created to overturn the earth boring unit 10. FIG.illustrates another method of constraining the phenolic friction disks48 and 50 to rotate with the clutch housing 18. Extensions 62 areprovided on the phenolic friction disks 48 an 50. They extend into thering of load bolts 42. Holes 64 are provided for the load bolts 42 whichthen act to both compress the clutch and constrain the phenolic frictiondisks 48 and 50 from rotating with the clutch plate 26. Again, theresilient disks 58 and 60 are provided behind the phenolic frictiondisks 48 and 50. Proper alignment of the input with the output portionsmay be achieved by the alternate method illustrated in FIG. 5. A capbearing 66 is employed with a socket 68. The cap bearing is centered inthe clutch plate 26 and is anchored thereto. The cap bearing 66 providesa positive alignment force to retain the driving and driven portions inproper relative position.

To adjust the clutch, the load bolts 42 are uniformly torqued to drawthe backplate 44 toward the front plate 36. The clutch plate 26 is thusbetween the friction disks 48 and 50 and the resilient backing disks 58and 60. Because of the compressive nature of the resilient backing disks58 and 60, the loading through the bolts 42 will take place through agreater travel of the back plate 34 than would be necessary withoutdisks 58 and 60. Consequently, any increase in the compression of thevarious disks will be less dependent upon any unit of motion of the loadbolts 42 in the present invention.

Thus, a clutch is provided which acts to reduce the transmitted shockloads, reduces the effect of misalignment, and is easier to properlyadjust.

Having fully described the invention in connection with the presentlypreferred embodiment together with modifications thereof, it is to beunderstood that our invention is not limited to said embodiment ormodifications but rather is of the full scope of the appended claims.

We claim:

1. A slip clutch for a horizontal earth boring machine, said clutchcomprising;

a clutch plate,

a compression means,

two friction disks located within said compression means, said disksbeing in compressive contact with said clutch plate and beingconstrained to rotate with said compression means, and

resilient backing for said friction disks between each said frictiondisk and said compression means.

2. The device of claim 1, wherein said compression means comprises;

a front plate,

a back plate, and

means for tying said front plate to said back plate so as to compresssaid included friction disks, clutch plate and resilient backingtherebetween.

3. A slip clutch for a horizontal earth boring machine, said clutchcomprising;

a clutch plate,

a compression means,

two friction disks located within said compression means, said disksbeing in compressive contact with said clutch plate and beingconstrained to rotate with said compression means,

resilient backing for said friction disks, and

pins extending into said compression means, through said resilientbacking and into said friction disks to prevent relative rotation ofsaid friction disks with respect to said compression means.

4. The device of claim 1, wherein said friction disks extend to engagesaid compression means to prevent relative rotation of said frictiondisks relative to said compression means.

5. The device of claim 1, wherein said slip clutch further comprises themeans for physically maintaining alignment between said clutch plate andsaid compression means.

6. The device of claim 5, wherein said alignment means comprises a capbearing fixed to said drive disk in a socket fixed to said compressionmeans.

7. The device of claim 1, wherein said resilient backing is Neoprene.

8. A slip clutch comprising;

a front plate rigidly fixed to one side of the drive train, a back plateconstrained to move with said front plate,

tying means to forcibly draw said back plate toward said front plate,and to preventrelative rotation of said back plate relative to saidfront plate,

two friction disks'respectively attached to said front plate and saidback plate,

resilient backing material positioned between each of said frictiondisks and said front plate and said back plate respectively, and

a metal disk located between said friction disks and attached to theother side of the drive train.

9. The device of claim 8, wherein said slip clutch further comprises ameans for physically maintaining alignment between said front plate andsaid metal disk.

10. The device of claim 9, wherein said alignment means comprises a capbearing rigidly fixed to one side of said drive train and a socket toreceive said cap bearsaid socket being rigidly fixed to the other sideof the drive train.

11. The device of claim 8, wherein said backing material is Neoprene.

12. A slip clutch comprising;

a front plate rigidly fixed to one side of the drive train, a back plateconstrained to move with said front plate,

tying means to forcibly draw said back plate toward said front plate,and to prevent relative rotation of said back plate relative to saidfront plate,

two friction disks respectively attached to said front plate and saidback plate,

resilient backing material positioned between each of said frictiondisks and said front plate and said back plate respectively,

a metal disk located between said friction disks and attached to theother side of the drive train, and pins extending into said fricitondisks through said resilient backing material and into said front plateand said back plate respectively to prevent relative rotation of saidfriction disks with respect to said front plate and said back platerespectively.

13. The device of claim 8, wherein said friction disks extend about saidtying means so as to prevent relative rotation between said tying meansand said friction disks.

14. A slip clutch for a horizontal earth boring ma- 5 chine, said clutchcomprising;

a clutch plate,

a compression means,

two friction disks located within said compression means, said disksbeing in compressive contact with said clutch plate, resilient meanslocated between said friction disks and said compression means foraxially supporting said friction disks against said clutch plate, and

means for preventing shear loadings and. friction surface forces on saidresilient means.

The device of claim 14, wherein said compression means comprises:

a front plate,

a back plate, and

means for tying saidfront plate to said back plate so as to compresssaid included friction disks, clutch plate and resilient meanstherebetween.

16. A slip clutch for a horizontal earth boring machine, said clutchcomprising;

a clutch plate, a

a compression means, said compression means including a front plate, aback plate and means for tying said front plate to said back plate,

a first friction disk, said first friction disk being in contact withsaid clutch plate and being positioned between said clutch plate andsaid front plate,

- a second friction disk, said second friction disk being in contactwith said clutch plate and being positioned between said clutch plateand said back said friction disks and said compression means. 50

1. A slip clutch for a horizontal earth boring machine, said clutch comprising; a clutch plate, a compression means, two friction disks located within said compression means, said disks being in compressive contact with said clutch plate and being constrained to rotate with said compression means, and resilient backing for said friction disks between each said friction disk and said compression means.
 2. The device of claim 1, wherein said compression means comprises; a front plate, a back plate, and means for tying said front plate to said back plate so as to compress said included friction disks, clutch plate and resilient backing therebetween.
 3. A slip clutch for a horizontal earth boring machine, said clutch comprising; a clutch plate, a compression means, two friction disks located within said compression means, said disks being in compressive contact with said clutch plate and being constrained to rotate with said compression means, resilient backing for said friction disks, and pins extending into said compression means, through said resilient backing and into said friction disks to prevent relative rotation of said friction disks with respect to said compression means.
 4. The device of claim 1, wherein said friction disks extend to engage said compression means to prevent relative rotation of said friction disks relative to said compression means.
 5. The device of claim 1, wherein said slip clutch further comprises the means for physically maintaining alignment between said clutch plate and said compression means.
 6. The device of claim 5, wherein said alignment means comprises a cap bearing fixed to said drive disk in a socket fixed to said compression means.
 7. The device of claim 1, wherein said resilient backing is Neoprene.
 8. A slip clutch comprising; a front plate rigidly fixed to one side of the drive train, a back plate constrained to move with said front plate, tying means to forcibly draw said back plate toward said front plate, and to prevent relative rotation of said back plate relative to said front plate, two friction disks respectively attached to said front plate and said back plate, resilient backing material positioned between each of said friction disks and said front plate and said back plate respectively, and a metal disk located between said friction disks and attached to the other side of the drive train.
 9. The device of claim 8, wherein said slip clutch further comprises a means for physically maintaining alignment between said front plate and said metal disk.
 10. The device of claim 9, wherein said alignment means comprises a cap bearing rigidly fixed to one side of said drive train and a socket to receive said cap bearing; said socket being rigidly fixed to the other side of the drive train.
 11. The device of claim 8, wherein said backing material is Neoprene.
 12. A slip clutch comprising; a front plate rigidly fixed to one side of the drive train, a back plate constrained to move with said front plate, tying means to forcibly draw said back plate toward said front plate, and to prevent relative rotation of said back plate relative to said front plate, two friction disks respectiveLy attached to said front plate and said back plate, resilient backing material positioned between each of said friction disks and said front plate and said back plate respectively, a metal disk located between said friction disks and attached to the other side of the drive train, and pins extending into said friciton disks through said resilient backing material and into said front plate and said back plate respectively to prevent relative rotation of said friction disks with respect to said front plate and said back plate respectively.
 13. The device of claim 8, wherein said friction disks extend about said tying means so as to prevent relative rotation between said tying means and said friction disks.
 14. A slip clutch for a horizontal earth boring machine, said clutch comprising; a clutch plate, a compression means, two friction disks located within said compression means, said disks being in compressive contact with said clutch plate, resilient means located between said friction disks and said compression means for axially supporting said friction disks against said clutch plate, and means for preventing shear loadings and friction surface forces on said resilient means. 15 . The device of claim 14, wherein said compression means comprises: a front plate, a back plate, and means for tying said front plate to said back plate so as to compress said included friction disks, clutch plate and resilient means therebetween.
 16. A slip clutch for a horizontal earth boring machine, said clutch comprising; a clutch plate, a compression means, said compression means including a front plate, a back plate and means for tying said front plate to said back plate, a first friction disk, said first friction disk being in contact with said clutch plate and being positioned between said clutch plate and said front plate, a second friction disk, said second friction disk being in contact with said clutch plate and being positioned between said clutch plate and said back plate, a first resilient disk, said first resilient disk being positioned between said first friction disk and said front plate, a second resilient disk, said second resilient disk being positioned between said second friction disk and said back plate, and means for preventing relative lateral movement between the front and back faces of each of said resilient disks.
 17. The device of claim 16 wherein said means for preventing relative movement between the front and back faces of each of said resilient disks includes rigid links preventing relative rotational movement between said friction disks and said compression means. 